I don't think any of the MK-II's are adjustable. You'll have to go back to the tang safety version that was discontinued in the early 90's to get an adjustable trigger.
The Mk-II's were inconsistent, many were just fine, others needed work, but could be tweaked even though there were no adjustments. The new Hawkeye uses basically the same trigger, it is usually much better out of the box than the older MK-II's